Hi all, another post of interest from another list, this time
the Artmetal mailing list. Charles
From: Horton@gnn.com (Barbara Horton Rockwell)
Subject: tumblers
mind, except the door. It will have to be on the side of
the drum, and intend to cut it out with a torch. My question is, given
the kerf which will result from the cut, how does one obtain a tight
seal on this door when closed? I’m thinking of some sort of gasket, but h
aven’t explored that yet. Also, any advise on the speed of
rotation which is desirable? I assume a slow rotation, say 100 or less rpm.
How about what abrasive(s) to use? Are wooden paddles on the inside
sufficient to effect good tumbling action?
Door: you must be planning on rotating your tumbler in a linear
fashion. We have many tumblers. The most aggresive is a
closed tumbler with doors on the side. Do you need a good seal
because you will be tumbling wet? Ours has crank down doors with
a gasket and 2 large bolts, one on either side ofthe door, with
star shaped nuts.
another approach is to rotate with the end open, and the entire
barrel tilted, as a cement mixer would. 5 of our tumblers are
actually made from cement mixer barrels we got cheap. 5 are
made from joint compound pails, another is a ‘real’ tumbler,
hexagonal, but still rotating in cement mixer fashion. doors for
those, if needed, can be made from plywood and just fit over the
end. The one mentioned above with side doors is a pain to load
and unload and to check to see when parts are ready to remove.
Dumping is a real uisance as your dump pan must be directly under
the door as it faced the ground, and you must therefore have the
tumbler high enough to allow clearance for the dump pan. The open
end ones tilt forward and dump into washtubs with homemade
riddles.
RPMs–100 is WAY too fast.
Noise: We recently converted many of our tumblers to belt
driven. The noise from gear driven tumblers is deafening, and
over the long run irritating and harmful. we use gear reduction
to get the speed down.
more on noise: the large tumbler, which has doors on the side
of the barrel and has 2 compartments is lined with a non-rubber
substitute. I forgot which material we picked, but it used to be
liined with rubber, but rubber decays with the materials we
tumble in over time–LONG time, 10-15 years. Our hexagonal one
is also lined. You can buy 3/8" thick rubber and line it
yourself if you are careful. We have done it and patch ours too.
lining has great noise reduction properties, but even more
important it doesn’t bash the parts as badly.
Media: 4 of the 5 cement barrel tumblers use corn cob. mostly
for drying water or oil from the parts. Small amounts of parts.
The parts are protected that way. Cob is quiet, clean–hardly
any noise. One of the cement mixer tumblers uses a bit of cob but
most is full of parts (sand castings). We tumble castings in the
foundry to get the sand off before removing parting lines. That
process is INCREDIBLY noisy. Even the neighbors object. That is
because the tumbler is unlined and we are doing lots of parts.
If you used metal scraps as your media, I cannot think that level
of noise is good for you, and after years of noise exposure, let
me tell you it takes its toll. Ear ringing is no fun. Hearing
loss stinks.
in the 2 real tumblers we use stone–actual graded rocks that we
buy in one, and in the other, a plastic media. both are used
with water and the plastic gets a tiny amount of tumbling soap to
clean the parts. water quiets the process down too.
the trick is tumbling is to acheive slide. slide occurs when
the parts and the media slide from about 1/3 of the way up the
side to the bottom, as opposed to being hurled partway up and
falling in clumps to the bottom. slide protects parts and makes
sure that media rather than parts contact the other parts. when
it is working right, it makes a shih, shih, shih sound. tumblers
are never filled more than 1/4-1/3. Overfilling results in loss
of slide, and too little media results in bashed parts. if water
is used, in the style of tumbler with a door on the side, it
should cover the media about 1-2". in the other style tumblers,
only enough water to get good slide.
cob polishes nicely. I recommend it highly. it is cheap too.
1420, or #2 is a good size.
in our joint compound tumblers we use steel shot and mineral
oil. those tumblers have 2"x 1.5" high wide wooden paddles
mounted inside diagonally from the bottom to the open end. One
is all, I think. That works well too, they have to go really slow
or they spit shot at you, and they cannot be tilted down to
empty, due to the nature of the design and the lack of weight
that a plastic bucket can support. We used covers with large
shot (.080+) because of the flying shot problem but don’t need it
with the tiny shot. We reach in with a homemade rake and get
the oily parts out. shot is heavy and we don’t want to dump it
anyway. 3 barrels are linked together and 2 others work together
as they are small and we needed more capacity but didn’t want to
spend money for real tumblers. plus we used old motors and gear
reduction devices that were laying aroung to make them.
Most tumblers are on timers, but some are light switch type.
any other questions, feel free!
barb the tumbling maven.
Brain Press
Box 1624, Ste M, Calgary, Alberta, T2P 2L7, Canada
Tel: 403-263-3955 Fax: 403-283-9053 Email: @Charles_Lewton-Brain
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